I think that using the radio is just any other skill - you either use it or loose it. And that's particularly relevant when it comes to the radio, because using it often causes people lots of (almost certainly unnecessary) anxiety - so, since it's very easy to fly using the radio only very minimally, that's what lots of people do.
I think the most relevant thing from your post is that you say: "Luckily the controller was very patient with my weak radio strength (and skills I guess) and we had a very pleasant trip round a very beautiful part of the country. Thank you Mr Controller." Unfortunately, not all controllers are that understanding, but the vast majority of them are, and realising that is the key to having the confidence to give it a go, and fly through that bit of airspace instead of around it.
One hint when using the radio is to know what you expect ATC to say to you, and how you will reply, before you press the PTT button. In this respect, using the radio regularly is a big bonus. If you transit that MATZ or that bit of Class D every week or two, you'll soon get used to all the possible replies, and know how to respond to them. If the last time you called for a MATZ transit was a year ago, though, then the chances are you can't remember what reply ATC might give you.
FFF
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